Hello all! I just received my Altmill 4x4 this last week and got it set up and running over the weekend. I’ve had a few issues with the homing functions, etc. that I’ve worked my way through.
Everything seemed to be working fine, I could jog the spindle everywhere, X, Y, and Z axis worked great. So, I decided to give the break-in job a run, as recommended by Garrett at IDC Woodwork in this video: https://www.youtube.com/watch?v=W0f_tNwaTaw
Once the CNC started moving at greater speeds that what the jog functions move it at, I have found that I have a very heavy vibration on the right side Y-axis ball screw. It happens in the same area of the ball screw each time. It’s bad enough the vibration is visible. I followed the troubleshooting steps found here: Movement and Homing Troubleshooting, and while I did clear up some of it, it is still very present and very loud when the machine is running at speed. I’ve recorded some video of it and I’m hoping someone can set me in the right direction to get this fixed.
I’ve also gone over the machine to ensure that I didn’t miss any screws and they’re all tight, nothing was left loose.
OUCH !!! That is painful to watch and to listen to. There seems to be something on the ball screw where the noise is happening. It is quite noticeable. No clue if the noise and the crap on the screw are related.
What’s visible on the screw is grease that came shipped with it. That’s where the guide that the gantry attaches to and has the zerk fittings for grease. I figured it would spread out over time.
So sorry that is not normal and I know your pain since you just got it. I did an AI search for you. Sometimes it gives some nice feed back. Here you are:
The heavy vibration and loud chattering you are experiencing in a specific zone of your right-side Y-axis ball screw during higher-speed rapid movements is a known mechanical issue usually caused by component misalignment, mounting tension, or dry bearings. When the machine moves at rapid break-in speeds, any slight binding or parallel deviation across the length of the travel causes the ball screw to resonant or “whip”. [1, 2, 3, 4]
Follow these steps to isolate and resolve the vibration:
1. Perform a Gantry and Bearing Block Realignment
A common culprit is that the ball screw nut housing and the end bearing blocks are not perfectly parallel, binding the screw as the gantry moves into that specific zone. [1]
Loosen the ball nut screws: Find the four screws attaching the right-side Y gantry plate to the aluminum ball screw nut block. Loosen them by 1 to 2 full turns.
Loosen the end bearing blocks: Slightly loosen the fasteners holding the Y-axis end plates/bearing blocks at the front and back of the machine.
Settle the assembly: Physically jog or manually slide the gantry back and forth across the entire length of the Y-axis travel multiple times. Moving it directly into the vibrating zone while loose allows the hardware to settle into its natural, un-torqued “sweet spot”.
Retighten sequentially: Bring the gantry to one of the hard stops to keep it square. Tighten the four ball nut block screws completely. Next, jog the gantry directly next to the end bearing blocks before tightening them down. [1, 2, 3, 4, 5]
2. Verify Motor Coupler and End-Plate Seating
If the motor shaft and the ball screw are mating at a minute angle, it transfers a severe orbital vibration into the screw at high RPMs. [1, 2]
Loosen the set screw on the Y-axis motor coupler specifically on the motor shaft side (leave the ball screw side tight).
Ensure the motor and the Y-axis end plates sit completely flat and flush against the structural rails.
Push the coupler firmly toward the bearing to eliminate any axial play, then lock down the coupler set screws securely. [1, 2]
3. Check for Factory Defects or Assembly Flips
Check for a flipped nut block: Ensure your right-side ball screw assembly wasn’t accidentally installed upside down. If the grease nipple is facing inward or downward where it is impossible to access, the block must be unbolted and flipped 180 degrees so the wiper and bearings seat correctly.
Look for manufacturing bulletins: Sienci Labs previously identified specific batches where minor gantry plate hole misalignments caused binding. Inspect the right gantry plate to ensure the motor mounts fully flush without forcing the screws. [1, 2]
4. Flush and Lubricate the Ball Nut
A trapped piece of packing debris or a dry cluster of bearings inside the recirculating tracks will cause severe chattering at speed. [1, 2]
Pump a high-quality machine grease through the Zerk fitting on the right Y-axis ball nut.
Manually roll the gantry across the axis to evenly distribute the grease inside the ball tracks. [1, 2]
If the vibration persists in the exact same physical spot after complete unbolting and realignment, the ball screw shaft itself may be slightly bent from transit. You should roll the removed screw on a verified flat surface to check for a wobble and contact Sienci support for a replacement. [1, 2, 3]
Not long after setting up my AltMill 4 x 4 the same thing happened. Backing off the screws securing the right hand Y gantry support plate bearings and ballscrew coupler, then retightening them fixed the issue. Has not happened again.
I emailed support and they got back to me. The instruction video I was following said to use 20mm screws to attach the gantry carrier when it should have been 16mm screws. I swapped them out with the correct sized screws and now I having good vibrations.